Oil that is pumped from a producing oil formation at a remote well head is often stored on-site in a tank. The oil often contains large amounts of water and formation sand or proppant/frac sand. Over time, the oil, water and solid phases will separate out. The sand will collect at the bottom of the tank and the oil will float on top of the water. Other particulate matter such as shale and clay may also accumulate. A significant amount of oil may remain emulsified in the water and adsorbed on the particulate matter. In a typical field oil storage tank in the region of Innisfree, Saskatchewan, Canada, the non-aqueous components may have the following composition:
TABLE 1Oil/paraffin17.65%Asphaltene1.81%Carbonates0.34%Iron salts0.68%Insolubles79.52%
The insolubles consist primarily of silica sand.
To further collect and process the oil, it is necessary to separate the water and sand from the oil. The water and sand present disposal problems that must be addressed in a cost efficient and ecologically sound manner. Separating the sand and water from the oil waste has a number of advantages including recovery of a reusable product, reduction of waste storage costs and mitigation of toxic waste pollution. Major hydrocarbon producers are under increasing public and regulatory pressure to conduct their businesses in a manner that is as environmentally benign as possible. This has created a problem that was heretofore addressed by burying the mixtures or spreading the mixture on rural roads as a dust control agent. Since, burying or long-term storage is not longer a feasible solution, there has been created an imperative to resolve this issue.
This problem was partially solved by my invention entitled “Treatment of Oil, Water and Sand Mixtures” described in my Canadian Patent 2,196,522. This invention provides for chemical addition and describes a method and apparatus for treating oil, water and sand mixtures into separate components. However, this invention was designed to be stationary and feedstock has to be transported to the treatment site. Due to the remote nature of many oil and gas well fields, trucking oil, water and sand mixtures to a separation plant is prohibitively expensive. My co-pending patent application “Trailer Mounted Mobile Apparatus for Dewatering and Recovering Formation Sand” having a filing date of Oct. 29, 2003 and a Ser. No. 10/694,716, incorporated herein by reference addresses the problem of removing and dewatering sand from remote oil field storage tanks. However, it does not directly address the requirement of treating oil field storage tank effluent by chemical means to further promote separation of oil, sand and water. The additional of chemicals to the effluent from storage tanks is necessary in order for the process to work effectively.
Therefore, there continues to be a need, not heretofore known in the prior art, of a self-contained mobile chemical mixing and injection unit and method for using the same to enhance the remote processing of oil field storage tank effluent and in order to promote separation of sand, oil and water.